Electronic apparatus for controlling a machine



June 10, 1958 PE 2,838,653

ELECTRONIC APPARATUS FOR CONTROLLING A MACHINE Filed March 6, 1956 2 Sheets-Sheer; 1

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June 10, 1958 L. PERAS 2,838,653

ELECTRONIC APPARATUS FOR CONTROLLING A MACHINE Filed March 6, 1956 2 Sheets-Sheet 2 57 I '7 m;- m 2,99

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United States Patent ELECTRONIC APPARATUS FOR CONTROLLING A MACHINE Lucien Pras, Billancourt, France, assignor to Regie Nationale des Usines Renault, Billancourt, France, French works under the control and the authority of the French Government Original application January 10, 1955, Serial N 0. 480,947. gg'iggd and this application March 6, 1956, Serial No.

Claims priority, application France February 10, 1954 4 Claims. (Cl. 219-408) This invention relates to an electronic apparatus for controlling a machine, in particular a welding machine for sheet metal elements of automobile bodies.

An electronic apparatus for controlling a machine, notably a welding machine, which is designed to repeat on the one hand equal current-conducting time periods and, on the other hand, equal non-conductive time periods, is described and illustrated in the French Patent No. 1,099,933 of the Regie Nationale des Usines Renault, for Electronic Sequence Non-Synchrone Apparatus for Machines Performing a Plurality of Recurrent Complex Cycles. This apparatus provides the intermediate contacts of the cycle by means of thyratron tubes arranged in separate stages comprising circuit sections, so that the coils of electromagnet values and relays to be controlled are inserted in the anode circuits of the thyratrons, the latter supplying capacitors adapted to block and release the tubes of the other stages by acting on the grid potentials of these tubes. It is also well known to replace the control relay for the ignitron tubes by two power thyratron tubes (of type PL-lOS or othertype) with a tuned circuit operating from the starting point of the sinusoid. A dephasing circuit, so-called heat-contro is generally added to the tuned circuit. This apparatus is called synchronous control. In this case, certain circuit sections are arranged to form closed circuits in which a given portion of the cycle, for instance the control of the conductive and non-conductive periods, is repeated until the action produced by another partial circuit will discontinue the steps of the cycle portion taking place by blocking one or more tubes.

As a result, all the conductive periods are equal to one another and the non-conductive periods are also equal to one another, the respective cycle values being of course adjustable at will once for all for repeating a predetermined welding operation.

According to this invention, a machine for pulsation welding with decreasing cold periods is controlled from 4 an electronic apparatus having an asynchronous or synchronous sequence adapted to perform repeated and.

complex cycles of operation comprising time periods of same character but unequal durations. This apparatus comprises essentially a number of thyratron circuit sections of which some control the energizing windings of electromagnet valves and relays of the machine, other circuit sections being arranged to become alternately conductive and non-conductive in cascade so as to produce the pulsations, i. e. in the. specific application of the apparatus to a welding machine, the heat and cool times occurring within the total current passage interval.

The unequal time periods, for example the progressively decreasing cold time periods, are determined by means .of a vacuum electron tube (for example a triode, tetrode i or pentode) incorporated into the anode circuit of one .of the thyratron tubes and adapted, through the variation of its internal resistance, to modify from one pulsation to another of same character the discharge time of a capacitor controlling the value of the cold period.

An electronic apparatus according to this invention for controlling a welding machine of the pulsation welding type will be described hereafter with reference to the accompanying drawing forming part of this specification and showing diagrammatically, by way of example, the manner in which the invention may be carried out in the practice.

The wiring diagram (Fig. l-la) of the apparatus provided by this invention is shown in the drawing. The complete circuit is supplied with single-phase A. C. voltage from a transformer having four secondaries lTaSl to 1TaS4 each capable of 55 effective volts or 55 R. M. S. volts; this circuit comprises 17 electronic tubes of the thyratron type designated by the reference symbols TU1 to TU17, and a vacuum tube TU18. The circuit section of each tube comprises essentially a capacitor and a resistor in the anode circuit, a resistor in the grid circuit, and, accessorily, decoupling capacitors, potentiometers and reversing switches.

In order to aiford a clearer understanding of the principle according to which the apparatus operates, two circuit sections corresponding to the tubes TU1 and TUlS respectively will be described hereafter.

The circuit of the thyratron tube TU1 is fed with single-phase A. C. between the points 01 and 06. Its cathode circuit comprises a switch P between points 06 and 04 which is controlled by means of the treadle actuated by the operator of the machine, the treadle when depressed closing a holding contact 5Re2. A resistor 1R3 is inserted in the control grid circuit and a decoupling capacitor 1C3 is positioned between the cathode circuit and the grid circuit. The anode circuit of tube TU1 comprises a capacitor 1C7 disposed between the points 01 (transformer terminal) and 17 (anode), and a resistor 1R7 is connected across the capacitor terminals.

In the specific case of this tube, a pair of grid circuits extend from point 17, the one through the resistor 2R3 to the control grid of tube TU2 to permit, by suitably biasing this grid, to block and release the tube TU2, and the other through the reversing switch 17-44 and re sistor 4R3 to the terminal 43 of the control grid of tube TU4 so that the latter may be blocked and released through the action of the circuit of tube TU1. On the other hand, when the reversing switch connects points 01 and 44, the operation sequence is discontinued as the electrodes are maintained under pressure but without passing any welding current therethrough.

The vacuum tube TU18 is disposed in the anode circuit of the thyratron tube TU13 so that its anode will be connected to the anode of tube TU13 through a current rectifier x and to the positive terminal of a D. C. source y through a selection potentiometer P The cathode of the vacuum tube is connected on the one hand to the terminal 06 of the secondary winding 1TaS4 of the general supply transformer through a resistor 13R7 and, on the other hand, to the negative terminal of the D. C. source y through a resistor 18R1.

The circuit of the control grid of the vacuum tube TU18 comprises notably a capacitor 18C3 and a resistor 18R3, the terminal 184 therebetween corresponding to the terminal of a reversing switch 2Re controlled from a relay Re disposed in the anode circuit of tube TU16. The terminals 185 and 186 of the reversing contact represent the one the intermediate point of a D. C. voltage divider constituted by resistors 18R4 and 18115, and the other the intermediate point of a D. C. voltage divider comprising the adjustable resistors 18R7 and 18R8.

The discharge of capacitor 13C7 determining the nonconductive time period of the welding current by blockingthe thyratron tube TUS in the anode circuit comprising the welding relay ERcS, the variation in the suc cessive discharge times of capacitor ll3 C7 makes it possible to vary the successive cold times. The automatic variation in the discharge time of the capacitor is ensured through the variation in the internal resistance of the vacuum tube TU18 by the discharge of capacitor 18C3 through resistor 18R7. As the grid voltage of the vacuum tube TU18 varies more or less rapidly, the plate output and the anode voltage of the tube are thus influenced and the internal resistance of the tube is altered accordingly.

When the contact P between points 06 and ()4 is open, the actions produced by the diiferent circuit elements of this assembly are as follows:

' Tube TU1 is not conducting as the contact between points 06 and 04 is open.

Tube TU2 is conducting as its control grid receives the same potential as its cathode, so that it charges the capacitor 2C7 across the resistor 2R7.

Tube TU3 is non-conducting because, due to the conduction established in circuit TU2, its control grid has a negative potential relative to the cathode potential. Therefore, theelectromagnet valve coil EV is still nonenergized.

Tube TU4 is conducting like tube TU2 as its control grid and cathode are at the same potential. Consequently, this tube charges the capacitor 4C7 across the circuit comprising resistor 4R7, potentiometer 4P7, resistor 4R8 or switch 4K7.

Tube TUS is non-conducting as its anode circuit is open between the points 06 and 04 due to the opening of the treadle-actuated contact P. On the other hand, its control grid has a negative potential relative to the cathode potential due to the conduction of current through the circuit TUd] It will be noted that the screen grid is at the same potential as the cathode since it is connected to the anode circuit of tube TU13 and this tube is non-conducting, as will be seen presently.

Tube TU6 is non-conducting because its control grid is connected to the anode circuit TU4 and its potential is therefore negative with respect to the cathode potential due to the conducting state of tube TU4.

Tube TUll is non-conducting because, as in the case of tube TUS, its control grid is connected to the anode circuit of TUA and negative relative to the cathode due to the conducting state of circuit TU4. Moreover, it will be noted that the screen-grid of this tube TU11 has the same potential as its cathode since the tube TU13-to whose anode circuit it is connectedis non-conducting.

Tube TUIZ is conducting because tube TUI]. is nonconducting and its control grid, connected to the anode circuit of TUll, has the same potential as its cathode. The. screen grid is also fed with the same potential for, being connected to the anode circuit of the non-conducting tube TUlS, it has the potential of point 05. Ca pacitor 12C7 is thus charged through resistor 12R7, potentiometer 12P7, resistor 12R8 or switch 12K7.

Tube TU13 is non-conducting due to the fact that its control grid is at a negative potential relative to its cathode due to the conducting state of circuit TU12.

Tube TUlo is non-conducting as its grid has a negative potential relative to its cathode since tube TU12 is conducting, the reversing switch 1R2 being positioned as shown in the figure. The screen-grid of tube TU16 is W blocked due to the conducting state'of tube TU17..

4 1 state of tube TU6, its control grid and cathode being at the same potential, i. e. that of point 05. Consequently, the tube charges the capacitor 7C7 through resistor 7R7, potentiometer 7P7, resistor 7R8 or switch 7K7.

Tube TU? is not conducting since its grid has a negative potential relative to the cathode, because the circuit of tube TU7 is conducting.

Tube TUZt i is conducting because tube TUB is nonconducting. Capacitor 14C7 is thus charged through resistor MR7.

Tube TU15 is non-conducting because tube TU14 is conducting.

Tube TU9 however is conducting and charges the capacitor 907 connected thereto through potentiometer 9P7 and resistor 9R7. It will be noted that the screengrid of this tube is'constantly at the same potential as the cathode when the reversing switch V is positioned as indicated in the figure to connect points 96 and 06, this position corresponding to the flying or mass-production operation conditions. If switch V were positioned to connect points and 1537, the screen-grid of TU? would also be at the same potential as the cathode, tube TUlii being non-conducting.

Tube TUit is non-conducting because contact 01-491 operatively connected to contact fl4-t36 is open.

When the operator of the welding machine has depressed the treadle P, the closing of the contact between points b5 and @4 causes the cycle of operations of the machine to be initiated. The actions of the various elements constituting the circuit is then as follows:

Tube TUll is now conducting as its control grid is at the'same potential (that of point as as its cathode. Ca pacitor RC7 is thus charged through resistor 1R7 and blocks tubes TU2 and TU through its action on their control grids now at a negative potential relative to their cathodes. Due to this non-conducting state, capacitors 207 and 4C7 are discharged.

Capacitor 2C7 is discharged through resistor 2R7. When it has zero potential the control grid of tube TU3 is at the same potential as the cathode of this tube. Then tube TU3 becomes conducting and energizes the electromagnet valve coil EV, thus controlling the approaching movement of the welding electrodes. This is the beginning of the jointing or electrode-approaching operation, or squeeze time.

The capacitor 4C7 is discharged through resistor 4R7, potentiometer 4P7, resistor 4R8 or switch 4K7. The potentiometric adjustment makes it possible to retard and determine exactly the discharge time of capacitor 4C7 and, therefore, the time elapsing between the beginning of the jointing step and the beginning of the welding start. When the capacitor has zero potential, theorically tubes TUS, TU and TU11 are simultaneously conducting. in fact, the control grids of these three tubes, which are connected to the point 47 of the anode circuit of tube TU4, are nowat the same potential as their cathodes, i. e. the potential of point 66. The screen-grids of tubes TUS and TUll are also at the same potential as their cathodes, as tube TU13 is non-conducting.

Tube TUS now conducting will energize the welding relay SReS, switch CP being closed. Welding current is thus supplied to the electrodes. 1

Tube TU6 is conducting and commences to charge capacitor 6C7 through resistor 6R7, and simultaneously blocks the control grids of tubes TU7 and TU17, these grids passing to a negative potential relative to their cathodes due to the conducting state, in this circuit, of tube TU6. The blocking of tube TU7 permits the discharge of capacitor 7C7 through resistor 7R7, potentiometer 7P7, resistor 7R3 or switch 7K7. This is the beginning of the counting of the welding interval time. Regarding the tube TU17, its non-conducting state entails the discharge of capacitor 17C7 through resistor 17R7.

The conducting tube TU11 will initiate the charging.

'5 of capacitor 11C7 through resistor 11R7, thereby blocking the control grid of tube TU12 so that the latter will no more be conducting, and the capacitor 12C7 will thus be able to discharge itself through resistor 12R7, potentiometer 12P7, resistor 12R8 or switch 12K7. This is the beginning of the counting of the first heat time.

Capacitor 1707 in the meantime has been discharged to zero potential and tube TU16 becomes conductive, its screen-grid having the same potential as its cathode. As the winding of relay Re is energized, its contacts lRe, 2Re and 3R2 are reversed so as to connect the points 163 and 03, 184 and 186, 189 and the positive terminal a of the source of current y, respectively. The control grid of tube TU16 is thus kept to the potential of its cathode although the capacitor 12C7 is discharged and tube TU16 will remain conductive until its screen-grid attains a negative potential relative to its cathode. At the same time, the reversing of contact 2Re enables the capacitor 18C3 to discharge itself through the variable resistor 18R7.

When the capacitor 1-2C7 attains the potential 0, the tube TU13 becomes conductive and charges the capacitor 13C7 through resistor 13R7 and vacuum tube TU18, the resistance of this last-mentioned tube decreasing as the grid bias varies. The screen-grids of tubes TU5 and TU11 are thus blocked and these tubes become nonconductive. As a consequence, regarding the tube TUS, the welding relay SReS is de-energized. This is the end of the first heat time. However, the control grid of this tube remains at the potential of its cathode as long as the tube TUd is non-conducting. Regarding the nonconducting state of tube TU11, its consequence is to enable the capacitor 11C7 to be discharged through resistor MR7.

When capacitor 11C? attains its zero potential condition, tube TU12 becomes conductive, charges the capacitor 12C7 through resistor 12R7, potentiometer 12P7, re- :sistor 12R8 or switch 12K7, so that tubes TU13 and 'TUS are rendered non-conductive due to the blocking of the control grid of the former and to the blocking of the screen-grid of the latter.

The non-conductive state of tube TU13 causes the capacitor 13C'7 to be discharged through resistor 13R7 and vacuum tube T U18. This is the beginning of the counting of the first cool time. The duration of this cool time is conditioned by that of the discharge of capacitor 13C7 which in turn is a function of the internal resistance R1 of the vacuum tube TU18, this resistance depending itself on the grid potential K of this tube TU18.

When capacitor 13C? is brought to zero potential, tube TUS becomes again conductive and supplies energizing current to the welding relay SReS. This marks the end of the counting of the first cool time. The tube TU11 is also brought to its conducting state, capacitor 11C7 is charged through resistor MR7, and tube TU12 is again non-conducting, so that capacitor 12C7 may be discharged through resistor 12R7, potentiometer 12P7, resistor MR8 or switch 12K7. This is the beginning of the counting of the second heat time.

When capacitor 12C7 is discharged, tube TU13 is again conducting and charges capacitor 13C7 while precluding any conduction through tubes TU5 and TU11 due to the blocking of the relevant screen-grids. Meanwhile, the internal resistance of tube TU18 is still decreasing. Regarding the tube TUS, the blocking thereof causes the second heat time to end because the Welding relay SReS is not energied, whilst the blocking of tube TU11 enables the capacitor 11C7 to be discharged.

Tube TU12 becoming conductive, it charges again the capacitor 12C7, thereby reblocking the tubes TU13 and TU8.

The non-conductive state of tube TU13 perits the capacitor 13C7 to be discharged through resistor 13R7 and vacuum tube TU18. This marks the beginning of '6 the second cool time of the cycle,,the duration of this period being determined by the internal resistance of tube TU18.' Since the grid potential of this tube has passed from K to K the internal resistance will be R R Therefore, the second cool time will be shorter than the first one.

As already explained, the second cool time terminates exactly when the capacitor 13C7 is brought to zero potential. Then, tube TU5 becomes conducting and will energize again the welding relay SReS.

The cycle of the conductive and non-conductive irn pulses of the welding current is continued as described until the last heat time has been completed. As already indicated, this cycle commences with the blocking of tube TU12 and the discharge of capacitor 12C7, so as to bring the tube TU8 to its conducting state. Thus, the screen-grid of this tube is released when the capacitor 12C7 is discharged (at the end of the hot period) and its control grid is released when the capacitor 7C7 is brought to zero potential (end of the welding interval). Then, both tubes TU14 and TU9 are non-conductive.

The non-conductive state of tube TU14 enables the capacitor 14C7 to be discharged. When the zero potential has been attained by this capacitor, the tube TU15 charges the capacitor 15C7 and causes the tube TU12 to become non-conductive due to the blocking of its screengrid. Consequently, the welding relay SReS cannot be re-energized subsequent to the termination of the last hot period.

The non-conductive state in tube TU9 which, as already pointed out hereinabove, is due to the conduction brought about in tube TU8, causes the capacitor 9C7 to be discharged through resistor 9R7 and potentiometer 9P7.

When capacitor 907 is discharged, tube TU10 be comes conductive and charges the capacitor 10C7 and blocks the control grid oftube TU1. This is the beginning of the repetition time separating two successive welding cycles.

The electronic apparatus for controlling a welding cycle which is described hereinabove constitutes but an exemplary form of embodiment of the invention, as the latter is not limited to the arrangement shown and described herein. Thus, the apparatus may be used for controlling machines or mechanisms of any description, which operate in accordance with a complex cycle within which operations of unequal durations must be transformed.

Modifications and alternations may be brought to the apparatus described without departing from the spirit and scope of the invention, notably with a view to adapt this apparatus to a predetermined cycle of operations.

This application is a division of my application Serial No. 480,947, filed January 10, 1955.

I claim:

1. Apparatus for controlling the energization of a load circuit, comprising a source of current, a circuit closing relay having contacts operable to connect said load circuit to said source of current and operable to disconnect said load circuit from said source of current, a pluraiity of electron discharge devices for energizing said relay in successive intervals of time of equal duration when rendered conductive, means for rendering said discharge devices conductive in stages and in successive intervals of-equal time duration and means for controlling the periods of non-conduction in a predetermined time pattern of progressively decreasing time intervals in accordance with a predetermined law, whereby the disconnect periods of said relay correspond to said predetermined time pattern.

2. In a welding machine having welding electrodes and a source of welding current, an improved timing device comprising in combination a plurality of electron discharge devices connected in cascade for controlling the application of welding current to the electrodes, currentresponsive means connected to-be rendered operative by saiddischarge devices for intermittently connecting the welding current source to the electrodes in successive intervals of equal time duration in a given welding cycle, means to render the discharge devices conductive and non-conductive in stages so as to alternately energize and de-energize said current-responsive means, automatic means to control the non-conductive periods of time of said stages in a selected time pattern of progressively decreasing intervals of non-conduction, whereby the electrodes are provided with welding current in a selected pattern of successive hot periods of equal time duration and cool period of said electrodes between successive hot periods decrease progressively in time duration during the welding cycle.

3. In a welding machine having welding electrodes and a source of welding current, an improved timing device comprising in combination electrical space discharge devices connected in cascade for controlling the application of welding current to the electrodes, current-responsive means connected to be rendered operative by said discharge devices for intermittently connecting the welding current source to the electrodes in successive intervals of equal duration in a given welding cycle, means to alternately render the discharge devices conductive and non-conductive in stages so as to alternately energize and de-energize said current-responsive means, means comprising a control electrical space discharge device different from said first mentioned discharge devices connected for automatically controlling the non-conductive periods of time of said stages in a selected time pattern of progressively decreasing intervals of non-conduction, whereby the electrodes are provided with current in a selected time pattern of successive hot periods of equal time duration and cool periods of said electrodes between successive hot periods'decrease progressively in time duration during the welding cycle, a counting capacitor connected to be charged by said control discharge device and having connections for initiating the discharge of said discharge device stages, means to vary the internal resistance of said control discharge device thereby to 8 varythe charging rate of said capacitor, whereby the cool periods are determined as a function of the internal resistance changesin said control discharge device during a given welding cycle.

4. In a welding machine having welding electrodes, a source of welding current, and an electrode-moving mechanism for applying welding pressure to a workpiece to be welded, an improved timing device comprising in combination a plurality of electrical space discharge devices connected in cascade for controlling the application of welding pressure to the workpiece and the application of welding current to the electrodes, first current-responsive means connected to be rendered operative by said discharge devices for intermittently connecting the welding current source to the electrodes in successive intervals of equal time duration in a given welding cycle, second current-responsive means for actuating the electrode moving mechanism and connected to be energized by said discharge devices, means to render the discharge devices conductive and non-conductive in stages so as to alternately energize and de-energize said first currentresponsive means, means to first render one stage con ductive to energize said second current-responsive means 7 prior in time to the energization of said first current- References Cited in the file of this patent V UNITED STATES PATENTS Gross Apr. 14, 1942 2,540,514 Elliott Feb. 6, 1951 Rockafellow Oct. 30, 1957 

